Weight — Grade 3 Mathematics
In Grade 3, we use grams (g) and kilograms (kg) confidently, convert between them with decimal notation, and apply weight concepts to multi-step problems including shopping, cooking, and comparing heavy objects.
Grams and Kilograms
kg → g: multiply by 1 000
g → kg: divide by 1 000
Examples:
2.4 kg = 2 400 g | 850 g = 0.85 kg | 3 kg 250 g = 3.25 kg
| Object | Approx. weight |
|---|---|
| Postage stamp | ~1 g |
| Apple | ~150 g |
| Bag of flour | 1.5 kg |
| Suitcase (allowed) | 20 kg |
| Small car | ~1 200 kg |
Worked Examples
Convert: (a) 3.75 kg to g (b) 2 300 g to kg
- (a) 3.75 × 1 000 = 3 750 g
- (b) 2 300 ÷ 1 000 = 2.3 kg
A baker uses 1.4 kg of flour, 750 g of sugar, and 300 g of butter. What is the total weight of ingredients in kg?
- Convert all to g: 1 400 + 750 + 300 = 2 450 g
- Convert back to kg: 2 450 ÷ 1 000 = 2.45 kg
Aisha's suitcase weighs 18.4 kg. Her carry-on weighs 4 750 g. The total limit is 25 kg. Does she have room for a 1.2 kg gift?
- Convert carry-on: 4 750 g = 4.75 kg
- Current total: 18.4 + 4.75 = 23.15 kg
- Remaining: 25 − 23.15 = 1.85 kg
- 1.85 > 1.2 → Yes, the gift fits.
Practice Questions
1. Convert 5.6 kg to grams.
2. Convert 3 450 g to kg.
3. Which is heavier: 2.4 kg or 2 350 g?
4. A bag contains 6 equal parcels weighing 3.6 kg total. How much does each parcel weigh in g?
5. A recipe needs 250 g of nuts. How many grams remain from a 1.5 kg bag after making the recipe 4 times?
Key Points to Remember
- 1 kg = 1 000 g — this is the only conversion you need.
- kg → g: × 1 000. g → kg: ÷ 1 000.
- 3 kg 500 g = 3.5 kg = 3 500 g — three equivalent forms.
- Always convert to the same unit before comparing or calculating.
- Check answers with common sense: a pen weighs ~5 g, not 5 kg!